The present invention relates to rotors in synchronous machines. In particular, the invention relates to mounting rotor field winding and a field winding enclosure on a rotor.
Conventional generators have rotors with retaining rings to support field coil windings mounted on the rotor. Each rotor typically includes a cylindrical rotor core with axial slots to receive each coil turn of the field windings. During assembly, the winding is installed turn by turn into the slots of the rotor core. The field winding is typically assembled while it is being installed in the slots of the rotor core. The slots of the rotor receive the layers of the straight sections of the race-track shaped coil windings. The ends turns of the windings extend axially beyond both ends of the rotor core.
In conventional rotors, retaining rings are mounted over the end turns and on the rotor core. The retaining rings are short cylindrical structures that support the end turns with respect to the centrifugal forces that arise during rotor operation. The retaining rings are installed on the ends of the rotor core after the field windings are installed in the rotor slots. To reduce the circumference of the winding assemblies and rotor, a belt is wrapped around the winding assemblies to pull the winding coils together and eliminate clearances between the coil. During assembly, the metallic retaining rings are expanded by heat and then slid over the ends of the winding assemblies and rotor core. When the rings cool, they shrink to tightly fit on the rotor core. At normal operating temperatures, there is no clearance between the retaining rings and the end turns of the rotor windings.